where \(f,g,h\)  are assumed to be smooth and \(x(t)\in {\mathbb {R}}^n, u(t),y(t)\in {\mathbb {R}}\) . The notion of moment-matching is closely related to the steady-state response of the system with respect to signals generated by an exosystem as presented in [1]} and [2]}. In particular, it has been proposed in [1]} that the reduced model of (REF ) that matched with the moment generated by
\(\dot{w} = s(w), \qquad u = c(w),\) 
